New York: Andy Roddick's transition from the tennis court to the rocking chair was delayed when the former world number one reached the third round of the U.S. Open on Friday, joining a parade of former champions advancing at the year's final grand slam.

Roddick, who announced Thursday he would retire at the end of the tournament, served his way past rising Australian talent Bernard Tomic 6-3, 6-4, 6-0 in his second-round match at raucous Arthur Ashe Stadium.

One favourite who was shown the door was China's Li Na, who became the latest victim of British giantkiller Laura Robson.

None of Friday's array of former champions excited the passions of the Flushing Meadows faithful more than Roddick, the never-say-die Texan who never saw a fight he did not like.

Roddick, 30, blasted 13 aces in the one hour, 27-minute rout under the lights.

He said he became emotional 15 minutes before the match when he saw a tribute to his career being shown on a television in the locker room.

"Oh man, that was so much fun," Roddick told the crowd in his on-court interview. "I really appreciate that, thank you guys. I just wanted to come out and be aggressive.

"I'm going to try to stick around a little longer."

The defending champions at the National Tennis Center had little trouble advancing, as Djokovic blitzed Brazilian Rogerio Dutra Silva 6-2, 6-1, 6-2 in sun-drenched Ashe Stadium, while Stosur sent off American Vavara Lepchenko 7-6, 6-2 on the same court to reach the women's fourth round.

Gritty Victory

Robson's gritty 6-4 6-7 6-2 triumph over former French Open champion Li, who triumphed in Cincinnati earlier this month, also created a buzz at Flushing Meadows.

Robson sent four-times grand slam champion Kim Clijsters into retirement in the second round but her upset of ninth-seeded Li surely made believers of those who thought she might be a one-hit wonder.

Next up in the fourth round is Australian Stosur.

"I have had a fairly tough draw, haven't I?" the soft-spoken 18-year-old, who was born in Australia, told reporters with a laugh.

"You have to beat who is in front of you. ... That's what I managed to do so far. I play Stosur now, who is defending champ. That's going to be really tough."

At 2-2 in the third set, Robson thought she had broken serve but umpire Louise Engzell ruled that the point should be replayed, even though Li had missed with her return.

The 89th-ranked Robson, however, refused to bend, breaking Li's serve twice to lead 5-2 before serving out the match.

"I wouldn't say I wasn't distracted. I was a little bit annoyed," Robson said of the umpire's call. "But that's what happens from time to time, so you've got to deal with it."

Djokovic dropped just two games in his opening-round win over Italy's Paolo Lorenzi and Silva managed only three more as the second-seeded Serb was in a different class.

"I didn't know much about my opponent," said Djokovic. "Never saw him play. So that could have been difficult at the start in order to figure out what his game plan is. But I played well from the start to the end."

Stosur was broken in the opening game of her match, setting the tone for a gruelling first set, which lasted 59 minutes. But the Australian secured the tiebreaker 7-5 and blew through the second set over a frustrated Lepchenko in 29 minutes.

"As the match went on I probably became a little bit more comfortable, got used to her spin, and maybe the wind a little bit more," said Stosur, who lost only five games in her first two matches. "Once I got that first set then maybe I relaxed a little bit more."

Sharapova continued her imperious march through the draw as she crushed American college player Mallory Burdette 6-1, 6-1 to reach the fourth round.

The Russian, who has lost just seven games in her first three matches, next plays compatriot Nadia Petrova, a 6-4, 7-5 winner over Czech Lucie Safarova.

Del Potro, the 2009 U.S. Open winner, downed American Ryan Harrison 6-2, 6-3, 2-6, 6-2, while 31-year-old wildcard Hewitt, who won the title in 2001, outlasted Gilles Muller of Luxembourg, 3-6, 7-6, 6-7, 7-5, 6-4 in four hours, 35 minutes.